In the laboratory, tire manufacturing and design may include evaluating tire tread wear performance with road wheel testing. Usually large diameter road wheels, such as 3 meters, are used to minimize the drum curvature effects on the tire's contact area and pressure distribution within the contact area. Many test machines can apply forces to the tire that are typical of actual vehicle loads—such as the radial, lateral, braking, and driving forces.
An abrasive surface may be provided over the outer surface of the road wheel. As the tire is rotated in contact with this surface, microscopic particles of tread rubber are worn off. The rate of wear and the uniformity of the wear over the tire surface are measured in order to assure acceptable tread wear performance of the tire in consumer service. Most common abrasive surfaces used in the tire industry for laboratory tread wear testing of tires are various grits of commercially available sand paper with adhesive backing, which are chosen for their high level of abrasiveness and ease of attachment to the road wheel with no consideration of roughness values or the structure of actual pavements. Prior techniques for matching roughness values from actual pavements relied on mixing hard aggregates, such as silica sand, with an epoxy resin bonding agent, such as in Japanese Patent Application Publication No. JP 07-020030 (A), filed Jun. 16, 1993, now Japanese Patent No. JP 3234678 (B2), which is assigned to the assignee of the present application. Another technique involved using cast polyurethane to create a flexible material with texture of asphalt or concrete and adding grit to increase abrasiveness, such as in Walraven, Laboratory Tread Wear Simulation, MTS Systems Corporation, Oct. 17-20, 1995. The resulting material was designed for a tread wear machine that employed a small radius flexible belt test surface that came in contact with a test tire. Thus, the resulting material also had to be flexible in order to accommodate for the flexibility of the belt and prevent cracking of the wear surface. However, such technique was inferior to using adhesive-backed sand paper and suffered from unacceptable problems such as short service expectancy due to the flexibility and softness of the resulting wear surface.
In a different field of noise testing, sound signatures of various tires have been measured by bringing the tire in contact with a road wheel coated with a wear surface made from a cast of a road. However, such wear surfaces did not contain any aggregate and were not optimized for emulating the surface roughness characteristics of a broad range of actual road surfaces. Furthermore, such wear surfaces were not selected to provide an extended service life since they were not used for testing tread wear.